Radio receiving instrument for systems of broadcast distribution



-Ma s"; 1928. 1,669,327

E. E. CLEMENT RADIO RECEIVING INSTRUMENT FOR SYSTEMS OF BROADCAST DISTRIBUTION Filed May 20. 1924 4 Sheets-Sheet 1 May 8, 1928. 1,669,327

E. E. CLEMENT RADIO RECEIVING INSTRUMENT FOR SYSTEMS OF BROADCAST DISTRIBUTION Filed May 20. 1924 4 Sheets-Sheet P May 8, 1928 1,669,327

E. E, CLEMENT RADIO RECEIVING INSTRUMENT FOR SYSTEMS OF BROADCAST DISTRIBUTION Filed May 20, 1924 4 Sheets-Sheet 3 May 8,1928.

E. E. CLEMENT RADIO RECEIVING INSTRUMENT FOR SYSTEMS 0F BROADCAST DISTRIBUTION 4 Sheets-Sheet 4 Filed May 20, 1924 Patented May 8, 1928.

UNITED STATES 1,669,327 PATENT OFFICE;

EDWARD E. CLEMENT, OI WASIiING'ION, DISTBIlCT OF COLUMBIA, ASSIGNOB TO EDWARD F. COLLAIDAY, OF WASHINGTON, DISTRiCT OF COLUMBIA.

mm momma msrmmnu'r FOB SYSTEMS or BROADCAST DISTRIBUTION.

Application filed May 20,

The present invention relates to carrier current transmission systems and more partficularly-to a system of power supply there- The chief object of the invention is to provide a carrier current transmission system capable of being superimposed upon a system of distribution such as a telephone exchange system for the purpose of supplying power thereover, independently of and without interference with the transmission of telephone messages, for the operation of radio receiving apparatus or for both. the operation of radio receiying apparatus and signal transmission thereto in the form of modulations superimposed on the power supply.

Another object is to provide a system for transmitting power by a carrier wave and in a manner to combine the advanta es in power transformation attainable wit low frequency alternating current, with the advantages in segregation or differentiation in duplex transmission attainable with highfrequency or superaudible oscillating currents.

Other objects .of the invention will be apparent from the followin specification and drawings accompanying t e same.

In the drawings: Fig. 1 is a diagram showin 'my system of power supply applied to a te ephone line for operating a two-tube radio receiving set.

Fig. 2 is a diagram showing the system similarly. applied for operating a simple detector setl Fig. 3 is a modification of Fig. 2 in which the filament variable resistance is replaced by a variable connection with the primary of the power su ply induction coil.

Fig. 4 is a applied for the supply of power over a telephone line to a single tube regenerative set with loop antenna.

Fig. 4 is a diagram of an inductively coupled aerial and ground connection to be substituted for the loop in Fig. 4.

Fig. 5 is a diagram showing the system applied to a reflex receiving circuit.

Fig. 6 is a diagram showing an arrangement for applying the systemto the supply of both power and signal current to a simple detector set.

Fig. 7 is a diagram showing the system applied for the supply of both power and sigiagram showing the system.

'ried within considerable limits. frequencies. with wave lengths ranging from 1924. Serial No. 714,720.

nal current to a simple triode'tube receiving set.

Fig. 8 is a diagram showing the system used for the supply of power to a multi-tube, loud speaker set requiring different operating voltages.

Fig. 9 is a diagram showing the invention applied as in Fig. 8 with the additional feature of supplying si nal current in the form of modulations o the power supply current.

Referring to the drawings in detail: In

Fig. 1, 1 and2represent a pair of tele-.

phone lines leading from line terminal apparatus, represented by the jack J, at a telephone exchange, to a subscribers substation telephone set T connected to the line by conductors 3 and 4, through the radio frequency choke coils Sand 6 arranged to choke out the superaudio, oscillating power supply current. Bridged across the terminals of the telephone line at the subscribers station is a coil 7 and variable condenser 8, preferably adjusted to tune the line to a set superaudio frequency. At centr al, a high frequency generator 9 constitutes the source of high frequency superaudio power supply which is connected through transformer 10 and the line multiples 11-12 to the line wires 1-2. At

the subscribers station, the coil 7 constitutes the primary of a power transformer PT having a high voltage secondary coil 13 and a low voltage secondary coil 14, the low voltage coil 14. being connected to supply current to the filaments of the electron dis charge tubes 15 and 16, while the high potential coil 13 isconnected in the plate circuit of the tube '16, the tube 15- being a diode tube and the tube 16 a triode tube. The-generator 9 may be of, any known or suit-able type, such as the Alexanderson machi e, for generating superaudio current, th t is to say, alternating currents at frequencies above those ordinarily employed on telephone lines. I have found a suitable frequency for this purpose to be 20 kilocycles per second, although this may be va- At these 5.000 to 15,000 meters, transmission over the line wires is efiicient, and the transformers indicated at 10 and at PT may have a high reactanee resistance ratio, and deliver the necessary power without serious losses. I

contemplate using this power, as disclosed herein, for all purposes involved in receiv-- ing either by radio or carrier current at substations, including the carrying of modulations, and I have found that the closer my power transformers approach ordinary audio frequency, the more efiicient for the present purpose, will be the ordinary translating units which I prefer to employ. Thus, I preferably use transformers with iron cores. These transformers may be toroids, with iron dust cores, or they may have cores of very finely divided continuous bodies of very soft iron. The characteristics of such transformers are favorable for my purpose, the reactance curve of such a transformer designed for a minimum of 2,000 cycles, giving maximum ratio at 20,000, and thereafter falling away. I have found that these same transformers will carry radio frequencies and deliver more energy than air-core transformers, provided the iron in the cores be very finely divided and, the design be otherwise correct. Because the apparent resistance is higher than the actual ohmic resistance of the windings, increasing of course with the frequency, finer wire than usual. at low frequencies, can be employed, and considerable energy can be transmitted by a small unit.

In operation the circuits of Fig. 1 may derive their input of radio waves from any suitable collector, shown as an antenna 17, with a switch 18 by which it may be connected to any one of the condensers 19, 19 and 19 for tuning, tuning being further accomplished by means of the variometer coils 20, around which are connected the elec trodes of the diode tube 15. This acts as a detector. and has its plate circuit 21 extended through the primary winding of an audio frequency transformer 22, the secondary of which is connected to the grid circuit of the triode amplifying tube 16, the plate circuit 23 of which is extended through the coils of the receiving telephone 24 and the secondary 13 of the transformer PT. The filaments of both tubes are supplied with current from tertiary winding 14 on the transformer PT.

Details of the telephone operation in this circuit need not be given, it being sufficient to state that the telephone operation, both as regards the subscribers instrument T and the central office switchboard connections typified by the ark symbol J is the same as in all standard telephone exchange systems, and may be varied to suit circumstances. The principal point is that over the telephone line. and without disturbing the telephone service, I transmit superaudio alternating currents which through the transformer PT are propagated into the circuits of the radiophone set, at suitable voltages and in suitable volume for the several purposes required thereby. Thus, the primary winding 7 may be carrying a line voltage of 90; the secondary winding 13 may be carrying a plate voltage of 22 to 60; and the tertiary winding 14 may carry a filament voltage of say 1.1 to 3 volts, according to the tubes employed.

In order to produce very smooth action of the secondary induced currents, condensers may be bridged around the secondary and tertiary windings 13 and 14 if desired.

It will be remembered however, that the alternating current in point is superaudio, and in addition to this it may bear a different relation to the frequency of the carrier wave for which the receiving instrument is specially designed. For example, if we assume that the generator 9 is at a. central station which also contains the broadcasting apparatus and supplies either original broadcast matter, or regional distributionof' matter from distant points to the subscribers, then the particular wave length chosen for power transmission and the wave length chosen for radiation to the subscribers station, may be properly related so as to harmonize, as for example by making the short ether waves harmonics as regards other wave lengths of the long waves used for wire transmission. As will appear further in this specification, I also contemplate actually modulating the power transmitting waves, and these modulationswould be preferably the same as those being radiated through the ether.

Referring to Fig. 2, there is shown a modified circuit in which the central office is typified by spring jack J, a subscribers station by telephone X, a radio telephone receiver R, and the line by wires 1 and 2. In this case the transformer 10 has variable inductance and capacity for tuning, and receives its energizing current from high he quency alternator 9. The substation transformer PT is similarly tuned, and its secondary winding 13 is connected to the filament circuit of the diode tube 15", this tube being a simple detector without any amplification. The antenna connections are substantially the same as Fig. 1, and the headphone 24 is connected directly in the detector bridge around the inductance coils 20.

Fig. 3 shows the same parts as Fig. 2. similarly arranged except that. while in Fig. 2 a rheostat is shown in the filament circuit of the tube 15. in Fig. 3 this rhcostat is omitted and its function is perl'ornuul by the winding 13. of the transformer PT.

In Fig. 4 I have shown .a somewhat more elaborate circuit, although only a single triode tube is employed. The central office switchboard J, the transformer 10 and the generator 9 are indicated by the same symbols as before, the line wires 1 and 2 ex tend from a central to a substation X ill) equipped with a telephone T, and a radio telephone receiver R; and a' power transformer PT is provided, in a tuned bridge of the line around the telephone, for supply current to the tube circuits. A loop antenna 17 is shown in this case with a tuning condenser 25 and a triode detector tube 26. The secondary winding 13 of the transformer PT furnishes plate current as before, and the tertiary winding 14 furnishes filament current at a lower voltage, connection to the filament being made through a potentiometer 27, by which the circuits can be balanced. The telephone headset 24 is shown provided with the usual by-pass condenser 28, and it may be noted that this is understood to be used wherever necessary. It is not always shown, and is not always employed. The loop antenna 17 would only be useful in local receiving with this set, and it is to be understood that an outside antenna 17 may be employed without departure from the principles involved. Such a substitute antenna. is shown in Fig. 4

In Fig. 5 I have shown my invention applied to a reflex circuit, employing two tubes, one, 29, being a triode amplifier, and the other, 30, being a diode detector. The central ofiice switchboard J generator 9, transformers 10 and PT, line wires 1 and 2, and subscribers telephone T, are all substantially the same as before. The circuits fed by the secondary coil 13 and the tertiary coil 14 are the plate circuits and filament circuits respectively of the two tubes. 29 and 30. In operation, modulated radio waves are received on the input side from antenna 17, are passed through the tube 29 for amplification at radio frequency, and by means of the radio frequency transformer 31 are propagated into the plate circuit of the diode tube 30. This acts as a detector, and the rectified waves are communicated to the circuit 32, including the primary winding of the audio transformer 33, and suitable bypass condenser 34. The audio frequency modulations thus stripped from the carrier wave are propagated, through the circuit 35, back to the grid and filament terminals respectively of the tube 29, by which they are amplified and propagated through the plate circuit 36 of ths tube to the receiving telephone or equivalent It may again be remarked that the transformer winding '13 and also the re ceivin instrument 37 may be shunted by suitab e capacity, as well as the coil 14 if desired. a

Referring to Fig. 6, I'have therein shown a very sim 1e detector circuit with the same central 0 cc switchboard J, generator 9,

transformer 10, linesl and 2, subscribers telephone T, and power transformer PT, as heretofore described. The secondary and tertiary windings 13 and 14 are included in duced in the circuit 42, which will act to produce amaximum current the plate circuit with maximum effect in the telephone or equivalent instrument 24. It may be observed that the winding 13 is shown with more turns than the winding 14, because of the difference in potentials required by 'the plate and filament circuits. respectively. 7

Referring to Fig. 7, Ihave shown therein a simple circuit from conveying power for the central ofiice over line wires 1 and 2 to the substation X as heretofore described, the power waves being conveniently 'employed as carrier waves or signals or sounds to be communicated to theradio receiving instrument at the substation. Alexanderson or other suitable generator of high frequency waves is shown at 9, and in its circuit 43 is a suitable modulator shown as a telephone transmitter 44, the arrangement or connections being such that modulated high frequency waves are propagated through the transformer 10 into the line circuits 1 and 2 through the primary winding 7 of the substation transformer PT. The secondary and tertiary windings 13 and 14 are connected as before to the plate circuit and to the filament circuit respectively of the tube 45, which in this case is a triode de tector' tube. The coil 13 and the coil 14 have of course connections through the wire 46, whereby the grid of the tube 45 is exposed to variations in potentials correspondmg to the-modulations impressed upon the carrier wave in the circuit 43. Thus the same current transmitted from central over the line wires 1 and 2 furnishes energy to heat the filament of the tube 45, other energy to maintain the potential of the plate circuit of said tube, and modulations superposed upon the power waves, to eitectithe grid circuit and react upon the flow of electrons and the consequent flow of current in the plate circuit. Itis to be particularly observed that as the carrier wave transmitted from central to the substation over the wires 1 and 2 is at a superaudio frequency, it can have no effect of its own upon any apparatus connected with the circuit. Moreover, there can bc no interference or confusion as between the plate, grid and filament circuits by reason of alternating current being employed, because all the currents supplied to the different circuits,

' of standard and demonstrated apparatus operating at low frequencies of the order of 60 cycles per second, and have superimposed power modulations upon the initial carrier wave, which are stripped off said carrier at the substation, as modulations, and used for power purposes only. Suppose for example that the initial power current or power carrier wave is at a superaudio frequency of the order of 25 kilocycles per second, and suppose this power wave is modulated in a wave of the order of 60 cycles per second; then by transmitting this modulated current to the substation, the 60 cycle modulation may be taken OE and applied to the radiophone circuits through a suitable transformer designed for such low frequency, and obviously coming within the range of electrical efliciency which is possible with low frequencies. This modulated current may be ap lied to any of the circuits hereinbefore descri ed or to any others which are equivalent thereto; and obviously additional forms of modulations may also be imposed upon the carrier wave or power current, with the great advantage that since this current is at superaudio frequency, it can be segregated and will not affect any audio apparatus connected with the circuit.

The radiophone receiving apparatus R of this Fig. 8 is based on a disclosure in my prior copending application filed February 9. 1924, Serial No. 691,825, and in advance of this application based upon work done at the U. S. Bureau of Standards on a receiving set fed with alternating current at standard commercial frequency. The antenna and ground connections are the same as usual, the radio receiver R comprisin three stages of radio amplification, a crysta detector in a tuned circuit between transformers, and two stages of audio frequency transformation. the .output terminals of the righthand tube being connected to the pri mary of the audio transformer 40, the secondary of which goes to the armature coil of the loud speaker. The filament circuits of the five tubes shown are supplied from a pair of bus wires 41, bridged across the terminals of a winding 42 on the transformer ST. The plate circuits are supplied from a second winding 43, a Tungar tube rectifier 44 being interposed in this circuit, so that rectified current of the proper voltmeasa'r age goes to the plates. The filament of the Tungar tube is fed from a third wlnding a5, and finally energy is supplied to all the secondary windings by means of a primary winding 46 connected to the circuit 47 tuned by means of the inductance of coil 46 and the capacity of variable condenser 49 to the frequency, as for example, 60 cycles per second, with which the foregoing transformer and substation set are designed to be used. This frequency may of course be i'aried, and in some cases may even be made a radio frequency, in which case the transformer ST' would become the equivalent of the transformer PT shown in the other figures, in which the primary windings are connected directly to the line. Using power modulations on high frequency carrier current however, I put the primary of the coupler transformer PT and its variable condenser 50 across the terminals of the telephone T on the line wires 12. Radio choke coils 5 and 6 may be employed in the telephone branch as before if found necessary.

It will be understood that the bridge circuit 51 containing said primary and variable condenser is tuned to the frequency of the carrier current, with the usual allowance for side bands, etc. The secondary of the transformer PT is tapped, and connected in a circuit 52 so as to furnish filament current and also plate current for a Tungar tube rectifier and detector 48, by means of which the high frequency carrier current is filtered out or suppressed. and only the power modulations at low frequency such as 60 cycles are impressed upon the circuit 47. The circuit shown and the tube shown are of course only typical, such detector and filtering arrangement being well understood in general. Any suitalue rectifying arrangement which will give the same result may therefore be used in this connection. At the central station. generator 9 furnishes carrier current at high frequency such as for example, 20 to 60 kilocycles, while generator 90 iscoupled so as to modulate this first carrier current at the rate required by the substation transformer ST, as for example, 60 cycles per second.

In Fig. 9 I have shown a modification of the system of Fig. 8. in which not only power modulated carrier current is transmitted at super-audio frequency over a telephone line. but modulations or signals are also impressed upon said carrier current, which thus hecomes the vehicle for conveying said modulations to the input side of the subscribers rc-i ceiving instrument. The generator Q'fur nishes the carrier current at a suitable frequency, the generator 90 modulates said can rier current at much lower frequency, as for example, 60 cycles per second for a power wave; and the telephone transmitter 61, is coupled also to the carrier current circuit so as Ill to produce modulations therein corresponding to the signal orfspeech which it is desired to transmit to the substation. In this figure, T represents the telephone, supposed to be the same in substance as that shown diagramatically in Fig. 8. PT is the subscribers transformer coupler, 47 is the local power circuit supplying plates and filaments, and 53 is a tertiary winding on the transformer PT, adapted for connection with the input terminals of the coupler coil 54 of applicants radio set R. Switches 56 and 57 are shown by means of which the said coil 5et can be connected either to the winding 53 of the transformer PT, or to the antenna 17 and the ground, at will. lVhen these switches 56 and 57 are thrown so as to connect the receiver R V to the antenna and ground, the waves taken in on the input'side will be relatively short waves; while if said switches are thrown to connect the subscribers set with the line 12, the modulated carrier waves received will be relatively long waves, as of the order of 20 to 60 kilocycles, equivalent to wave lengths of 5,000 to 15,000 meters. The third switch 57 is therefore provided for covering and uncovering the winding of a load coil 58, to enable the instrument to operate on both long and short waves. This tuning may also be varied by the substitution of equivalents within the range of the art, without departure from the present invention.

It is to be understood that many changes and modifications may be made in the system thus described, without departure from the scope and purview of my invention. Thus, triode tubes may be substituted for the diode tubes suc as that marked 48 in Fig. 8 and others shown in Figs. 1, 2, 3, 5, and 6. Also, in accordance with the principle of using a rectifier in the plate circuit of the receiving set (see 44 in Fig. 8) such rectifiers may be provided for the plate circuits of Figs. 4 and 5 and 7, if desired, without departing from the invention. It is particularly to be noted that Figs. 6 and 7 are alike in respect of transmitting the speech or signal modulations over the wires from the central oflice, on the same carrier current which supplies energy for the substation filament and plate circuits.

. In Fig. 6 a diode detector tube is used, which is the simplest arrangement. In Fig. 7 a triode tube is employed. In all of these cases the oscillation produced in the tube itself, especially if in phase with the carrier current oscillations, will produce a rectified variable current in the plate circuit, although the electromotive forces produced in the secondary of the coupler transformer PT are alternating. Finally, it is within the scope of this invention to use a plurality of super-audio frequencies for power purposes, with or without special rectifiers at the subscribers station; or to use a pulsating current at su per-audio frequency, at a voltage suitable to the plate circuit at the substation, which may be modified by passing a number of the current-s through a transformer to supply a lower voltage for the filament circuit; or it is possible to use the same voltage, either pulsating or alternating, bridge the plate circuit directly across the terminals of the line so as to get the full voltage, and connect the filament through resistance; or it is well within the scope of my invention to use the periodic high frequency current transmitted over the line from central to furnish power for the filaments only, or the plate circuits only, or for the loud speaker, or for such other use with the dill'erent parts of the apparatus, severally or jointly as may be advantageous in any particular case. The characteristic of the plate circuit is relatively high voltage and relatively low current; the characteristic of the filament circuit is relatively high current and relatively low voltage. may be fed to the filament at the proper voltage, by the means herein described, and separate continuous battery current may be supplied to the plate either over the line from central or by means of a small booster battery included in series in the plate circuit, the same being bridged across the line for continuous line voltage as set forth in my prior application, Serial No. 699,023, filed March 13, 1924; or conversely the filament may be connected for line supply or for local battery supply, and the plate circuit supplied with high potential current by the methods herein described.

I claim:

1. A combined telephone and radio receiving system comprising the following instrumentalities: a telephone central station and telephone subscribers stations, wire circuits interconnecting the same, means for communicating electrical speech or signal waves over said wire circuits at telephonic or audio frequencies, radio receiving sets connected to said wire circuits comprising electron tubes in combination with responsive apparatus governed thereby, centralized means for supplying electrical operating energy for said subscribers telephone stations over said wire circuits, and centralized means for supplying electrical operating energy for said tubes over said wire circuits in waves at super audio frequencies.

'2. The system claimed in claim 1, With the additional element of means at each telephone subscribers station and means at each radio receiving set to differentiate between the respective currents intended for the respective stations and sets.

3. The system claimed in claim 1, with the additional element of means for impressing low frequency power waves as modulations on the high frequency energy carrier waves transmitted over the wire circuits, and means at the subscribers stations for strin- Current ping the power modulations ofi said carrier waves and feeding said power waves to the electron tubes for energizing the same.

4. The system claimed in claim 1, with electron tubes in the form of triodes, having filament, plate, and grid circuits, means at the central station for transmitting current waves at super 'audio frequency over the Wire circuits to the subscribers stations, means for modulating said waves in accordance with speech or signals, and means at a subscribers station for directing a portion of said modulated Waves to his input tube grid circuit, and means for directing other portions of said waves to the filament and plate circuits, respectively.

5. The system claimed in claim 1, having a generator of super-audio energy waves at the central station, means for modulating said waves as carrier waves at power frequency, other means for modulating the same carrier waves in accordance with speech or signals, means at a subscribeds station for stripping off said power modulations and directing them through the tube filament and plate circuits, and means for directing the speech or signal modulations through the input grid circuit.

6. The system claimed in claim 1, having a generator of super-audio energy and carrier waves at the central office, means for impressing power modulations on said waves, means for impressing audio frequency modulations thereon, means at a subscribers stationfor stripping off said power and audio waves and directing them through his tube set, and means for producing from said power waves currents of different voltages and directing the same through the filament and plate circuits, respectively.

In testimony whereof I hereunto afiix my signature.

EDWARD E. CLEMENT. 

